C64 Magic voice cartridge repair ideas

Hi.

I bought an unknown-condition Commodore 64 Magic Voice expansion. It was very cheap and I was curious :D

Although complete with box it appears to be faulty and I’d love to hear any ideas regarding futher troubleshooting.

When I plug it into my C64, the computer starts normally. However the SAY command causes a syntax error, so I presume the MV’s EPROM is not being mapped into memory (adding the SAY command to BASIC). Also trying to plug in a game cartridge to the MV, the computer does not start it but goes to the BASIC.

Looking at other older threads about these, the harder to get MOS 6525 appears to be fine: I have the C64 IEE-488 cartridge with the same chip and I swapped the 6525s for testing (IEE cartridge still works, the MV doesn’t with either chips).

I’ve also checked that the 640kHz oscillator is fine (although this ties to the TI speech chip only and I am not that far). The 27128 EPROM does verify against the BIN file at zimmers (https://www.zimmers.net/anonftp/pub/cbm/schematics/cartridges/c64/magic-voice/index.html, also chematics there). 

If I remove the LA05-124 Gate Array the C64 goes to a black screen, so it appears to be doing at least something. As far as I understand the schematics (at zimmers at link above), the gate array would appear the most likely suspect? It does appear to be known to go bad and there are some projects working on a replacement: https://www.forum64.de/index.php?thread/5049-magic-voice-plan. Has anyone here tried these (or other replacements, as the logic equations seem to be reverse-engineered, see the end of the thread)?

Happy new year (soon)!

Regards,
Ville